bpy.path.abspath is appears to be messing up
As someonewithpc said, .. means one directory up. Thus,

D:\Pictures\3D Models\Models\..\..\main_car\file.xml


is the same directory as

D:\Pictures\main_car\file.xml


although the path is overly complicated (not cleaned up).

You can shorten it by realpath() or abspath() from os.path:

import bpy
import os
os.path.realpath(bpy.path.abspath(your_path))